The C-076 family of compounds are a series of macrolides isolated from the fermentation broth of a strain of Streptomyces avermitilis. The C-076 compounds are characterized by having a 16-membered cyclic backbone substituted with a disaccharide and having a bicyclic spiroketal fused thereon. The compounds have the structure: ##STR1## wherein
the broken line indicates a single or a double bond;
R.sub.1 is hydroxy and is present only when said broken line indicates a single bond;
R.sub.2 is iso-propyl or sec-butyl; and
R.sub.3 is methoxy or hydroxy.
The C-076 compounds are named using a system of designations which corresponds to the structural variations as is set forth in the following table.
______________________________________ Compound R.sub.1 R.sub.2 R.sub.3 ______________________________________ A1a Double bond sec-butyl --OCH.sub.3 A1b Double bond iso-propyl --OCH.sub.3 A2a --OH sec-butyl --OCH.sub.3 A2b --OH iso-propyl --OCH.sub.3 B1a Double bond sec-butyl --OH B1b Double bond iso-propyl --OH B2a --OH sec-butyl --OH B2b --OH iso-propyl --OH ______________________________________
The above compounds are isolated from the fermentation broth of Streptomyces avermitilis using normal extraction and isolation procedures. The C-076 producing culture and the morphological characteristics thereof along with the procedures used for separating and isolating the C-076 compounds, are fully described in Great Britain Pat. No. 1573955.
The fermentation is carried out in an aqueous medium and includes an assimilable source of carbon, an assimilable source of nitrogen and inorganic salts and the fermentation is generally carried out under aerobic conditions. The specific nutrients and parameters for the fermentation are described completely in the above cited Great Britain patent.
The C-076 producing culture and a mutant thereof have been deposited in the permanent culture collection of the American Type Culture Collection, 12301 Parklawn Drive, Rockville, Md. 20852. The cultures are accessible under the accession numbers ATCC 31267 for the basic culture and ATCC 31272 (lyophilized tube) and ATCC 31271 (frozen vial) for the mutant. The C-076 compounds are potent antiparasitic agents with very broad spectrum anthelmintic, acaricidal, nematocidal and insecticidal activity.
Derivatives of the C-076 compounds have been prepared which also have considerable antiparasitic activity. In particular a mixture of at least 80% of 22,23-dihydro C-076 Bla and no more than 20% of 22,23-dihydro C-076 Blb is particularly effective and such a mixture has been given the generic name of ivermectin. Such compounds are disclosed in U.S. Pat. No. 4,199,569.